Here is a good tip if you downloaded a file it might have been a worm the only way to get ride of it is AVG Free Anti virus i no i had the same one probley .
Here is a link for the avg free.
AVG Anti-Virus Free Edition - Reviews and free AVG Anti-Virus Free Edition downloads at Download.com
Note:Make sure you update first be four use.
Chris b.....
Good Luck......